Fuel cells, similar to batteries, serve to directly convert chemical energy into electric power. The core piece of a fuel cell is the membrane electrode unit (MEA, membrane electrode assembly) consisting of an anode layer, a cathode layer as well as an electrolyte membrane separating the anode layer from the cathode layer. For generating power a fuel gas, for example hydrogen, is supplied to the anode layer, while an oxidation gas, for example air, is supplied to the cathode layer. This leads to an oxidation of fuel gas at the anode, wherein the electrons released by the fuel gas migrate from the anode to cathode where they reduce the oxidation gas via an electrically conductive connection. The negative oxidation gas ions generated during the process combine with the positively charged fuel gas ions. If, for example, hydrogen H2 is used as the fuel gas and oxygen O2 as the oxidation gas oxygen ions O2− in and on the anode layer will combine with hydrogen ions H+ to form water molecules H2O in case of a solid oxide fuel cell (SOFC). The energy released in the process can be used by connecting a consumer load between the anode and the cathode.
Since a single fuel cell only provides a low electric voltage (typically from 0.1 V to 1 V) usually a plurality of fuel cells is electrically connected in series in the form of a fuel cell stack so that the voltages of the individual fuel cells of the stack add up. In this case the cathode layer of one fuel cell is connected to the anode layer of the adjacent fuel cell via a bipolar plate, respectively.
Here the bipolar plate separates a flow area of the fuel gas from a flow area of the oxidation gas. Particularly bipolar plates having a meandering, undulating (corrugated steel-like) or zig-zag-shaped surface are proven. Bipolar plates of this type establish a contact to the adjacent fuel cell via extreme points (peak points) of their surface. The valleys positioned between the extreme points form ducts for guiding fuel gas or oxidation gas.